Lexus
Check Engine Light Questions

This page will list all the Check Engine Light questions and answers asked
of us pertaining to Lexus vehicles. Some models include the ES300, IS250, and
others.

Question:
I have a 1996 Lexus ES300 & the engine light came on. Upon
further investigation & using a Digital Car Reader it promted me with a
code P0402. Can you help in proper procedures in checking and
replacing failed component. Thanx, Ross - December 2008

Answer: Hi Ross. A P0402 code is Exhaust Gas Recirculation
Flow (EGR) Excessive Detected. The issue is with a part of the EGR
system. It could be the EGR valve itself, a plugged port, problems with the
solenoid, etc. I don't have diagnosis instructions specific to your car, you'll
want to get your hands on a quality ES300 repair manual for your Lexus for proper
instructions to follow. This article may also be of help, although it's not
model specific either - http://www.obd-codes.com/p0402
Good luck.

Question:
PUT NEW EXHAUST ON MY LEXUS GS400 1998 ENGINE LIGHT CAME ABOUT 65 MILES AFTER
I PUT IT ON BUT CAR RUNS GREAT WHAT CAN IT BE. IS THERE ANY WAY TO MAKE ENGINE
LIGHT GO OFF. - Kathy, October 2008

Answer: Hi Kathy. The first thing that comes to mind is that
there could be an exhaust leak somewhere. What you'll need to do next is get
the codes read. I can't offer much more than that. The problem could be that
an oxygen sensor was damaged or has failed, there could be an exhaust leak,
etc. It could also just be a coincidence that the engine light came on after
you had that work done (considering the code didn't come in immediately after
you picked it up). Getting the car's check engine codes read will help figure
out what's wrong. More
info here.

Question:
I have a 2002 Lexus ES 300 65K miles. Went up the mountain to Flagstaff from
Phoenix and the check engine light came on halfway there. Got back home,hooked
up my code reader and it showed PO 172. My research says its a 'transmission
fluid termperature sensor circuit low input'. What does that mean and what should
i do next? Thanks! - Mark, September 2008

Answer: Hi Mark. The description for a P0172 code is System
Too Rich (Bank 1). Code P0712 is Transmission Fluid Temperature
Sensor Circuit Low Input. Now I'm confused as to which code you have!
If it's a P0172, I'm not going to reinvent the wheel, just check out this good
article on P0172 -- [OBD-Codes.com
P0172]. If it's a P0712 article, the first thing you should do is check
the transmission fluid level and make sure it's OK. If there are no symptoms
you could wait a few days to see if the code goes away or you could clear the
code using your code reader. It may be an intermittent thing. If you're really
adventurous you could inspect the transmission and ensure all wiring & connections
are not loose or broken. The P0712 code refers to the circuit and a low input,
so I'd focus on the wiring & connectors. Good luck!